In an insulated type power semiconductor module used for a power conversion device such as an inverter, a wiring pattern is formed over a metal plate, serving as a heat radiation plate, through an insulation layer, and a power semiconductor element that performs a switching operation is disposed on the wiring pattern. Such a power semiconductor element is connected to external terminals and is molded by resin. In a power conversion device in which a switching operation with large current and high voltage is performed, a surge voltage (ΔV=L·di/dt) is generated due to a time rate of current change di/dt when the power semiconductor element is switched off and a parasitic inductance L contained in the power conversion device, and the surge voltage is applied to the power semiconductor element. As the parasitic inductance L increases, a surge voltage larger than a breakdown voltage of the power semiconductor element may be generated and thus may cause destruction of the power semiconductor element. Therefore, reducing inductance is requested in power conversion devices and reducing inductance is requested also in power semiconductor modules.
A power semiconductor module has been developed in which a plurality of power semiconductor elements are arranged in parallel in a package and a plurality of external terminals are disposed, and in which terminals of the plurality of power semiconductor elements are each separately connected to the external terminal in the package (e.g., see Patent Document 1). Also, in the module shown in Patent Document 1, the external terminals through which principal current flows are disposed in a vertically-stacked manner and bonding wires are disposed so as to cancel magnetic fluxes generated by the principal current, thereby reducing the inductance.